Abiotic environmental stresses, such as drought, salinity, wind, heat, and cold, are major limiting factors of plant growth and crop yield. Prolonged or continuous exposure to drought conditions causes major alterations in the plant metabolism that ultimately lead to cell death and, consequently, losses in crop yield. High salt content in some soils results in less water being available for cell intake; thus, high salt concentration has an effect on plants similar to the effect of drought on plants. Under freezing temperatures, plant cells lose water as a result of ice formation within the plant. Because crop damage from abiotic stresses is predominantly due to dehydration, water availability is an important aspect of the abiotic stresses and their effects on plant growth. Losses in crop yield of major crops caused by these stresses represent a major economic factor and contribute to food shortages in many underdeveloped countries.
Most plants have evolved protective mechanisms against dehydration caused by abiotic stress. However, if the severity and duration of the abiotic stress conditions are too great, the effects on development, growth, and yield of most crop plants are profound. Developing plants efficient in water use is therefore a strategy that has the potential to benefit human life. Many agricultural companies have attempted to identify genes that could confer tolerance to abiotic stress responses, in an effort to develop transgenic abiotic stress-tolerant crop plants. For example, the genome of the plant model Arabidopsis was the first to be sequenced and released by 2000. Although some genes that play a role in stress responses or efficient water utilization in plants have been characterized, the characterization and cloning of plant genes that confer the desired stress tolerance and/or efficient water utilization characteristics remain largely fragmented and incomplete.
The sunflower belongs to the Asteraceae family, whose members represent 10% of the flowering plants. However, the genome sequence of this species is largely unknown and the huge quantity of expressed sequence tags (ESTs) from Helianthus (sunflower) species available in public databases have not yet been well explored.